package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, String value, Long time, TimeUnit timeUnit) {
        this.stringRedisTemplate.opsForValue().set(key, value, time, timeUnit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit timeUnit) {
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(timeUnit.toSeconds(time)));
        //写入Redis
        this.stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, long timeout, TimeUnit unit) {
        //1. 从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(keyPrefix + id);
        //2. 判断是否存在
        if(StrUtil.isNotBlank(json)){
            //3. 存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if(json != null){
            return null;
        }
        //4. 不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5. 数据库不存在，返回错误信息
        if(r == null){
            stringRedisTemplate.opsForValue().set(keyPrefix + id, "",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6. 数据库存在，将数据存入redis，返回数据
        stringRedisTemplate.opsForValue().set(keyPrefix + id, JSONUtil.toJsonStr(r), timeout, unit);
        //8.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R, ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, long timeout, TimeUnit unit) {
        //1. 从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(CACHE_SHOP_KEY + id);
        //2. 判断是否存在
        if(StrUtil.isBlank(json)){
            //3. 存在，直接返回
            return null;
        }
        //4. 命中，需要将数据反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((String) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5. 判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            //5.1 未过期，直接返回店铺信息
            return r;
        }
        //5.2 已过期，需要缓存重建
        //5.2.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //5.2.2 判断是否获取锁成功
        if(isLock){
            //5.2.3 成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(keyPrefix + id, r1, timeout, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }

        //8.返回过期的商铺信息
        return r;
    }

    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }
}
